1. Field
Apparatuses and methods consistent with the present invention relate to processing a digital picture, and more particularly, to color rolling suppression.
2. Description of the Related Art
Color rolling means a situation in which a color temperature of a picture periodically varies when a moving picture to be stored in a National Television System Committee (NTSC) format is taken by a fixed digital picture processing device such as a closed-circuit television (CCTV). The color rolling is caused by variation of the amount of illumination input in each frame of the moving picture due to a difference between an alternating current (AC) power frequency (60 Hz) for power supply to a light source such as a fluorescent light and a sampling frequency (59.94 Hz) of the moving picture. Accordingly, as shown in FIG. 8, the moving picture alternately shows different colors such as blue and green. The occurrence of color rolling is not limited to the case of using the fluorescent light. Color rolling as described above may occur when the operation frequency of a light source is not the same as the sampling frequency of the moving picture. For example, color rolling may also occur when a light-emitting diode (LED), a semiconductor light source, etc. using alternating power is used as a light source during taking a moving picture.
Methods for reducing color rolling include a method using an automatic aperture lens and a line lock method for preventing color rolling by adjusting a sampling frequency of an image to a power frequency of a fluorescent light. However, these methods require additional costs.
Although there are signal processing methods such as a method performing auto white balance (AWB) at a high speed and a method compensating an average value of a blue (B) channel, it is difficult to expect remarkable improvement in performance from these signal processing methods. In addition, when there is a moving object, the color of an image of the moving object may be biased to a particular color.